Heretofore there have been known as processes for producing alcohols an indirect hydration process in which an olefin is absorbed by sulfuric acid and the resulting sulfuric acid ester is hydrolyzed to obtain an alcohol; and a direct hydration process which utilizes a solid acid or an aqueous acid solution, for example a process of hydration of an olefin which utilizes a solid acid especially a cation exchange resin as a catalyst and a sulfone as a reaction solvent (British Pat. No. 1,518,461).